<!DOCTYPE html>
<html lang="en">

  <head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>案例三</title>
  </head>

  <body>

  </body>
  <script>
    /*  var num = 10;

    function fn() {
      console.log(num);
    }
    fn(); */
    // 案例4
    /*  f1();
     console.log(c);
     console.log(b);
     console.log(a);

     function f1() {
       var a = b = c = 9;
       console.log(a);
       console.log(b);
       console.log(c);
     } */

    //执行过程
    function f1() {
      /* 
      var a = b = c = 9;相当于
      var a=9;b=9;c=9;a为局部变量，而b,c是全局变量
      */
      //var a = b = c = 9;
      var a = 9;
      b = 9;
      c = 9;
      console.log(a); //9
      console.log(b); //9
      console.log(c); //9
    }
    f1();
    console.log(c); //9
    console.log(b); //9
    console.log(a); // Uncaught ReferenceError: a is not defined
  </script>

</html>